Showing papers by "University of Lleida published in 2007"

Perceived e‐service quality (PeSQ)

Abstract: Purpose – The objectives of this article are to develop a multiple‐item scale for measuring e‐service quality and to study the influence of perceived quality on consumer satisfaction levels and the level of web site loyalty.Design/methodology/approach – First, there is an explanation of the main attributes of the concepts examined, with special attention being paid to the multi‐dimensional nature of the variables and the relationships between them. This is followed by an examination of the validation processes of the measuring instruments.Findings – The validation process of scales suggested that perceived quality is a multidimensional construct: web design, customer service, assurance and order management; that perceived quality influences on satisfaction; and that satisfaction influences on consumer loyalty. Moreover, no differences in these conclusions were observed if the total sample is divided between buyers and information searchers.Practical implications – First, the need to develop user‐friendly ...

Evenness drives consistent diversity effects in intensive grassland systems across 28 European sites

Abstract: 1 Ecological and agronomic research suggests that increased crop diversity in species-poor intensive systems may improve their provision of ecosystem services. Such general predictions can have critical importance for worldwide food production and agricultural practice but are largely untested at higher levels of diversity. 2 We propose new methodology for the design and analysis of experiments to quantify diversity-function relationships. Our methodology can quantify the relative strength of inter-specific interactions that contribute to a functional response, and can disentangle the separate contributions of species richness and relative abundance. 3 Applying our methodology to data from a common experiment at 28 European sites, we show that the above-ground biomass of four-species mixtures (two legumes and two grasses) in intensive grassland systems was consistently greater than that expected from monoculture performance, even at high productivity levels. The magnitude of this effect generally resulted in transgressive overyielding. 4 A combined analysis of first-year results across sites showed that the additional performance of mixtures was driven by the number and strength of pairwise inter-specific interactions and the evenness of the community. In general, all pairwise interactions contributed equally to the additional performance of mixtures; the grass-grass and legume-legume interactions were as strong as those between grasses and legumes. 5 The combined analysis across geographical and temporal scales in our study provides a generality of interpretation of our results that would not have been possible from individual site analyses or experimentation at a single site. 6 Our four-species agricultural grassland communities have proved a simple yet relevant model system for experimentation and development of methodology in diversity-function research. Our study establishes that principles derived from biodiversity research in extensive, semi-natural grassland systems are applicable in intensively managed grasslands with agricultural plant species.

Monothiol glutaredoxins: a common domain for multiple functions.

Abstract: Monothiol glutaredoxins with the CGFS sequence at the active site are widespread among prokaryotes and eukaryotes. Two subclasses exist, those with a single glutaredoxin domain and those with a thioredoxin-like region followed by one or more glutaredoxin domains. Studies in Saccharomyces cerevisiae have demonstrated the role of the Grx5 protein in the biogenesis of iron-sulfur clusters. Grx5 homologues in other eukaryotes could carry out similar functions. Two S. cerevisiae monothiol glutaredoxins with the thioredoxin-like extension, Grx3 and Grx4, are modulators of the transcriptional activator Aft1, which regulates iron uptake in yeast. The human PICOT protein is a Grx3/Grx4 homologue with the same hybrid primary structure that regulates protein kinase C activity and may participate in physiological processes such as control of cardiac function. Therefore, monothiol glutaredoxins share a common basic structural motif and biochemical mechanism of action, while participating in a diversity of cellular functions as protein redox regulators.

PAPER PRESENTED AT INTERNATIONAL WORKSHOP ON INCREASING WHEAT YIELD POTENTIAL, CIMMYT, OBREGON, MEXICO, 20–24 MARCH 2006 Sink limitations to yield in wheat: how could it be reduced?

Abstract: Ponencia presentada al International Workshop on Increasing Wheat Yield Potential, CIMMYT, Obregon, Mexic, del 20 al 24 de marc de 2006.

Persistent neuropsychological deficit in euthymic bipolar patients: executive function as a core deficit.

Abstract: OBJECTIVE To characterize neuropsychological deficits during the euthymic phase in a sample of bipolar outpatients treated with lithium as the principal mood-stabilizer medication. We sought to determine cognitive functioning of typical bipolar outpatients treated in clinical settings. METHOD Forty-four stable outpatients, fulfilling criteria of bipolar disorder (DSM-IV), were consecutively recruited from a defined catchment area and compared with 46 healthy matched controls in 2003. Patients were remitted for at least 3 months and euthymic (Hamilton Rating Scale for Depression score < 8 and Young Mania Rating Scale score < 6 for at least 3 months). They were receiving lithium as monotherapy (45.5%) or combined with other psychotropic medication (54.5%). Neuropsychological assessment was performed by means of a neuropsychological test battery tapping into the main cognitive domains (executive function, attention, processing speed, verbal memory, and visual memory). RESULTS Multivariate analysis of variance showed that euthymic bipolar patients performed significantly worse than controls in measures of executive function (F = 2.57, df = 4,82; p = .04) and inhibition (F = 3.83, df = 2,84; p = .03), after controlling for subclinical symptomatology, years of education, and premorbid intelligence quotient. Processing speed also differed significantly between groups (F = 3.73, df = 2,84; p = .03). The subgroup of patients on lithium monotherapy (45.5%) differed significantly from healthy matched controls on tasks of lack of inhibition (F = 5.8, df = 2,36; p = .007). Executive tasks showed between-subject effects. CONCLUSIONS These results suggest that impaired executive function and loss of inhibition might be an important feature of bipolar disorder regardless of the severity of the disease or the effects of medication. Also, these executive-type cognitive traits may constitute an endophenotype for further studies on the etiology of bipolar disorder.

Differential effects of vitamin D analogs on vascular calcification

Abstract: We tested the effects of calcitriol and its analog paricalcitol on VSMC calcification in vitro and in vivo. For that reason, cells and animals with five-sixths nephrectomy were treated with both compounds. Calcitriol, but not paricalcitol, increased VSMC calcification in vitro and in vivo independently of calcium and phosphate levels. This increase in calcification was parallel to an increase in the RANKL/OPG ratio. Introduction: Vascular calcification is a common finding in patients with endstage renal disease. Furthermore, those patients often present secondary hyperparathyroidism, partly because of a decrease of calcitriol synthesis on the kidney. Thus, one of the main therapeutic options is to treat those patients with calcitriol or analogs. However, this treatment presents unwanted side effects, such as increases in vascular calcification. Materials and Methods: We tested the effect on vascular smooth muscle cell (VSMC) calcification of calcitriol and one of its analogs, paricalcitol, in vitro and in vivo in animals with endstage renal disease. Results: Calcitriol increased calcification of VSMCs cultured in calcification media. This effect was not present when cells were incubated with paricalcitol. Furthermore, only cells incubated with calcitriol showed an increased RANKL/ osteoprotegerin (OPG) expression. Animals with renal failure treated with hypercalcemic doses of calcitriol and paricalcitol showed an increase in systolic blood pressure. However, diastolic blood pressure only raised significantly in those animals treated with paricalcitol. This effect led to a significant increase in pulse pressure in animals treated with calcitriol. The increase in pulse pressure was likely caused by the extensive calcification observed in arteries of animals treated with calcitriol. This increase in calcification was not seen in arteries of animals treated with paricalcitol, despite having similar levels of serum calcium and phosphorus as animals treated with calcitriol. Furthermore, the decreases in serum PTH levels were similar in both treatments. Conclusions: We conclude that paricalcitol has a different effect than calcitriol in VSMC calcification and that this could explain part of the differences observed in the clinical settings.

Can wheat yield be assessed by early measurements of Normalized Difference Vegetation Index

Abstract: An early prediction of crop biomass at maturity and yield is important in different circumstances. The use of spectral reflectance indices, such as the Normalized Difference Vegetation Index (NDVI), has been proposed as a fast, nondestructive way of estimating crop growth capacity. In this study, we examined whether NDVI assessment relatively early in the crop cycle may be useful for predicting final biomass and yield in wheat. To that end, NDVI was measured and biomass quantified regularly from tillering to maturity for six different wheat genotypes grown under a contrasting range of N and water availabilities. In addition, final biomass and yield were measured at maturity. In line with expectations from the literature, we found that NDVI at milk-grain stage was well correlated to final yield and biomass. However, it was also observed that NDVI at the onset of stem elongation was also reasonably correlated to both attributes. Because crop growth in wheat from the end of tillering to anthesis is related to the determination of grain number and yield, we propose the use of NDVI at the onset of stem elongation as a complementary criterion for establishing the required late crop management (N fertilisation, irrigation) practices.

When is stream invertebrate drift catastrophic? The role of hydraulics and sediment transport in initiating drift during flood events

Abstract: Summary 1. The term ‘catastrophic drift’ is used to describe the large-scale displacement of invertebrates that occurs during periods of increased river discharge. However, the physical processes that lead to animals entering the water column at such times remain poorly understood. Specifically, the hypothesis that the movement of bed sediments during floods triggers a large increase in drift has lacked a rigorous field test. 2. Using a portable flume, the hydraulic conditions and rates of bedload transport associated with small, frequent floods were created in situ within a reach of a gravel bed river. Experiments focussed on the patches of fine sediment which are the dominant source of bed material transported during small floods. The flume produced near bed velocities of up to 2 m s−1 over the patches, increasing shear stress, initiating sediment transport and causing invertebrates to enter the drift. 3. The total number of individuals lost from the bed, as well as the taxonomic composition of the drift, were influenced strongly by shear stress and bedload. The rate of loss from the bed was low at shear stresses <9 dynes cm−2 (0–4 individuals min−1 from the 0.5 m2 flume bed area). Once shear stress exceeded 9 dynes cm−2, the threshold that resulted in consistent bedload transport from the patches, the rate of loss of animals increased to a maximum of 56 individuals min−1. When bedload transport rates were at their highest, the taxonomic composition of the drift was more similar to the benthos than it was to the drift observed when bed material was stable. 4. Absolute rates of bedload transport created by the manipulations were extremely low (<7 g m−1 s−1) and typical of those measured during small, frequent floods. Events of this magnitude do not break up the armour layer across the reach as a whole and so exposed patches of fine sediment are the principal source of bedload material. Consequently, discharge events not considered as disturbances in geomorphic terms may initiate frequent episodes of so-called ‘catastrophic drift’ from patches of stream bed.

Soil organic carbon storage in mountain grasslands of the Pyrenees: effects of climate and topography

Abstract: The prediction of soil C stocks across the landscape has been increasingly studied in many areas of the world. Soil organic C storage in mountain areas is highly heterogeneous, mainly as a result of local-scale variability in the soil environment (topography, stoniness, parent material) and microclimate. The aims of the present study are to estimate soil organic C stocks (SOCS) in mineral soils of high-altitude grasslands of the Pyrenees and determine whether climatic and topographic variables can be used as predictors of SOCS and organic C content in the surface soil horizons of these ecosystems. For that purpose we sampled 35 soil profiles in subalpine and alpine grasslands including a range of altitudes, slopes and aspects. We analysed the soils for stoniness, bulk density, total C, texture, and C-to-N ratio and determined topographical variables. We used georeferenced climatic information for climatic descriptions of the sites. SOCS were highly correlated with soil depth. However, we were not able to predict soil depth by using environmental and topographic variables. In spite of this fact, altitude and aspect explained 41.2% of the SOCS variability while summer temperature and precipitation combined with aspect explained 56.9% of the variability of the organic C content of the surface layer (OC). The SOCS were low at high altitudes, probably as a result of an overall temperature limitation of net primary productivity. Under these conditions, the effect of aspect was small. The highest SOCS occurred at the lowest altitudes for ENE or WNW aspects, showing sharper decreases towards the south than to the north. The harsh climatic conditions and low-plant productivity that occur at the northern slopes reduced SOCS at the highest altitudes. In contrast, southern aspects showed similar organic C content along the altitudinal gradient. The OC variability in the surface soils not explained by climatic or topographic variables was partially related to the characteristics of soil organic matter, which may depend on the plant communities.

The Well-Being of 12 - to 16-Year-Old Adolescents and their Parents: Results from 1999 to 2003 Spanish Samples

Abstract: This study adopts satisfaction with life as a whole and satisfaction with specific life domains as indicators to analyse the relationships between the well-being of 12 to 16-year-old adolescents and some related constructs such as self-esteem, perceived control and perceived social support. Well-being indicators from a 2003 Spanish sample using an 11-point scale (N = 1,634) are compared with an equivalent 1999 Spanish sample using a 5-point scale (N = 1,618). The different results obtained from the 2003 sample with a Principal Component Analysis (PCA) using a shorter and a longer list of life domains are also discussed. A sub-sample of the adolescents’ results from the 2003 sample are compared with their parents’ answers, using the same well-being indicators. Using a list of 8 life domains, and despite the change of scale used, overall results show no relevant changes in adolescents’ satisfaction with life domains between 1999 and 2003 in Spain and are in agreement with normative data expected from western societies [Cummins: 1998, Social Indicators Research 43, pp. 307–334; Cummins et al.: 2001, Australian Unity Well-being Index (Australian Centre on Quality of Life, Deakin University, Melbourne)]. Adolescents’ overall life satisfaction has been shown to correlate consistently with the other well-being related constructs. However, it clearly decreases with age over the period studied. The results also show that increasing the list of life domains has a major impact on the structure of the results obtained. When we compare results from parents with those from their own child, outstanding differences in well-being appear between generations: few domain satisfaction dimensions show significant correlation between parents and children and more than 20% of the population studied shows high discrepancies in the answers in four domains.

Dietary Protein Restriction Decreases Oxidative Protein Damage, Peroxidizability Index, and Mitochondrial Complex I Content in Rat Liver

Abstract: Caloric restriction (CR) decreases oxidative damage, which contributes to the slowing of aging rate. It is not known if such decreases are due to calories themselves or specific dietary components. In this work, the ingestion of proteins of Wistar rats was decreased by 40% below that of controls. After 7 weeks, the liver of the protein-restricted (PR) animals showed decreases in oxidative protein damage, degree of membrane unsaturation, and mitochondrial complex I content. The results and previous information suggest that the decrease in the rate of aging induced by PR can be due in part to decreases in mitochondrial reactive oxygen species production and DNA and protein oxidative modification, increases in fatty acid components more resistant to oxidative damage, and decreased expression of complex I, analogously to what occurs during CR. Recent studies suggest that those benefits of PR could be caused, in turn, by the lowered methionine intake of that dietary manipulation.

Dimensionality of the Rosenberg Self-Esteem Scale and its relationships with the Three-and the Five-factor personality models.

Abstract: We investigated the dimensionality of the French version of the Rosenberg Self-Esteem Scale (RSES; Rosenberg, 1965) using confirmatory factor analysis. We tested models of 1 or 2 factors. Results suggest the RSES is a 1-dimensional scale with 3 highly correlated items. Comparison with the Revised NEO-Personality Inventory (NEO-PI-R; Costa, McCrae, & Rolland, 1998) demonstrated that Neuroticism correlated strongly and Extraversion and Conscientiousness moderately with the RSES. Depression accounted for 47% of the variance of the RSES. Other NEO-PI-R facets were also moderately related with self-esteem.

Long‐term yield and water use efficiency under various tillage systems in Mediterranean rainfed conditions

Abstract: Conservation tillage (CT) can be beneficial for soil, water and soil organic matter conservation in Mediterranean areas that are prone to soil erosion and where water availability for crops is the main factor for sustainability. CT is the best option to protect the soil from erosion, improve infiltration, reduce soil evaporation and so conserve rainwater to increase crop water use (WU) and also water use efficiency (WUE). While CT can play an important role in reaching the stability and sustainability of these agricultural systems, performance depends upon the choice and adoption of an appropriate soil management (tillage) system. In rainfed areas of the Ebro Valley, winter cereals are the main crop sown. This paper presents the results of 15 years of research in different soil and climatic conditions of the area of CT on water conservation, WU and WUE. Long-term experiments, comparing different tillage systems, were established in 1987, 1990 and 1992, at three locations in the Ebro Valley, chosen according to their degree of aridity (Selvanera, Agramunt and El Cano´s). Results reveal that CT was most effective in increasing yield under the driest conditions at Agramunt (10–15%), still effective with a smaller advantage under slightly wetter conditions at El Cano´s (5–10%) but ineffective at Selvanera, the wettest site. CT only increased WU in some years at Agramunt and never at the other two sites. The benefits of CT to both increased yield at Agramunt and El Cano´s were determined by improved WUE arising from changes in the pattern of WU before and after anthesis.